Just like how Microsoft retired the Microsoft Authenticator password manager Chrome extension, Microsoft is also retiring password and payment support in Microsoft Authenticator for Android and iOS, meaning it will soon function as an Authenticator app only:
https://support.microsoft.com/en-us/account-billing/changes-to-microsoft-authenticator-autofill-09fd75df-dc04-4477-9619-811510805ab6
Their answer, of course? Use Edge. The Password Manager in Edge mobile now supports autofill across the OS.
Kinda sad to me that Microsoft took these free platform agnostic solutions, and then just kinda pushed them into Edge. At least Edge now supports being your OS-wide password manager if necessary.